(1) Field of the Invention
This invention generally relates to warning and alarm systems and more particularly to railway warning and alarm systems that can detect a railroad track misalignment.
(2) Description of the Prior Art
Various alarm systems have been proposed for detecting a number of conditions in a railroad system including broken tracks, train collisions and other faults. For example, U.S. Pat. No. 3,696,243 (1972) to Risley discloses a broken rail detector in which a transmitter provides coded pulses to a relay. The relay, intermittently and according to the code, applies electrical energy to each track at different polarities. A receiver receives the coded energy at a position remote from the transmitter. Any change in the received code indicates to the transmitter that some change in track characteristics has occurred.
U.S. Pat. No. 4,207,569 (1980) to Meyer discloses a railroad radio frequency waveguide for conducting radio frequency signals ahead of a train and along a railroad line comprising the ballast, ties and rails. Reflections received by a receiver on the train represent changes in the characteristics impedance of the waveguide. These reflections may be compared to anticipated reflections in order to detect improper conditions such as a broken track or the presence of another train.
U.S. Pat. No. 4,306,694 (1981) to Kuhn discloses a dual signal frequency motion monitor and broken rail detector. A highway crossing warning system for monitoring the motion and predicting the time of arrival of an approaching train at the highway crossing and for detecting the presence of a broken rail in the approach zone is acheived by feeding dual frequency signals into the track rails and measuring the track impedances at the two frequencies and the phase angle of the lower of the two frequencies.
U.S. Pat. No. 4,886,226 (1989) to Frielinghaus discloses a broken rail and/or broken rail joint bar detection system. This system detects rail breaks in dark territory track sections, i.e., track sections that do not have a signaling system. A communications link may exist between the ends of the track sections.
U.S. Pat. No. 4,932,618 (1990) to Davenport et al. discloses a sonic track condition determination system. Sonic transponders mount on a train and the track upon which it rolls and transmit and receive sonic vibrations along the track. Information currently being transmitted electrically may also be transmitted sonically. Since the track interferes with the sonic vibrations more than it does with an electrical signal, the condition of the track may also be determined. Specifically, this invention utilizes six steps including (1) impressing a first sonic vibration in a predetermined form on the track at the train, (2) receiving the first sonic vibration from the track at the point on the track distant from the train, (3) impressing a second sonic vibration, in a predetermined form, on the track at the point of the track distant from the train, (4) receiving the second sonic vibration from the track at the train, (5) comparing the first or second sonic vibration as received with the corresponding sonic vibration as predetermined, and (6) converting the comparison of the vibration as received with the corresponding vibration as predetermined into a determination of the condition of the track between the train and the point on the track distant from the train.
U.S. Pat. No. 4,979,392 (1990) to Guinon discloses a railroad track detector that mounts on a track vehicle and uses the track ahead or behind the vehicle as a transmission line for a high frequency signal. The transmission line has a known characteristic impedance and a condition of no track fault. The impedance is included in a bridge network that is excited with the high frequency signal. Bridge imbalance indicates a track fault that can be a complete or partial short circuit or open circuit. The bridge excitation is applied to the track through moving contacts, like brushes, ahead of the front wheels or behind the last wheels. The shunt effect of the wheels close to the brushes is eliminated by a tuning impedance that creates an effective infinite impedance to the portion of the track between the moving contacts and the shunting wheels.
U.S. Pat. No. 5,713,540 (1989) to Gerszberg et al. discloses a method and apparatus for detecting railway activity by means of a highly reliable, early warning system that can provide efficient detection of railway activity in which an acoustic sensor circuit coupled to the railway detects sound waves resulting from physical vibrations on the tracks. An acoustic analysis of the detected sound waves identifies any suspect conditions and generates an alarm signal accordingly. An acoustic signal processing unit stores detected sound waves in a sound file for quick retrieval and analysis. The alarm signal may be transmitted over any communications system to the central control office and to trains traveling on the dangerous track. The stored sound files may be locally retrieved or downloaded to a remote location over a cellular system thus enabling the analysis of the actual sound generated by the dangerous condition to determine the cause therefore.
Generally speaking, the foregoing references can be categorized as suggesting the detection of an imbalance in the electrical characteristic of two rails. The Meyer patent also discloses the concept of using an imbalance to signal a fault. Each of these systems, however, requires reasonably expensive installations particularly requiring equipment at various sites. Moreover, these patents disclose systems that will detect major faults, as a broken track. However, there are a number of situations in which mere misalignment of a track may cause a derailment. Such misalignments can often occur at bridges, for example, where the tracks on the bridge span may be swung out of position or moved out of alignment with the tracks on land. It is important when the bridge is closed that the tracks exactly align in both the horizontal and vertical orientations. None of these references appears to disclose or suggest any modality that is sufficiently sensitive to detect any such misalignment. What is needed is a system that can be used to detect such misalignments and can be easily installed in the vicinity of a track subject to such a misalignment, as at any bridge.
Therefore it is an object of this invention to provide a method and apparatus for detecting track misalignments.
Another object of this invention is to provide a method and apparatus for detecting track misalignments that is efficient to operate.
In accordance with one aspect of this invention, the detection of a railroad track misalignment in a predetermined track area includes directing RF energy to a proximally positioned rail remotely from the predetermined track area whereby the track acts as a traveling wave antenna. The RF signal is then detected at a remote site proximate the site of the potential misalignment. An alarm responds to the level of the received signal when the received signal exceeds a predetermined value.